If you didn't actually delete the files from within LW's options, or from shared/saved folders outside of LW then the files should still be around. Just choosing not to share something won't delete it...just means that the files won't show up in LW's library.

Did you use your computer's search to look for some of the file names?

Have a look at this thread - there's info about the location of saved & shared folders in the newer versions of LW. Since you didn't tell us which 4.16 version you're using, I'm not sure where the saved & shared folders will be located. But that info's in the thread below...find those folders on your computer & see whether your son's music's all there.
If you've updated LW and can't find your downloads!